(, "special treatment") is any sort of preferential treatment. However, the word Sonderbehandlung was used as an euphemism for mass murder by Nazi functionaries and the SS, who commonly used the abbreviation S.B. in documentation. It first came to prominence during Action T4, where SS doctors killed mentally ill and disabled patients between 1939 and 1941, and was one of a number of nonspecific words the Nazis used to document mass murder and genocide. Another notable example was . This term was also used to imprecisely refer to the equipment used to perpetrate their crimes, such as gas chambers and Zyklon B. The true meaning of was widely known in the SS, and in April 1943, Heinrich Himmler was so concerned about the security of it that he had it redacted in a secret report. Berel Lang states that disguised language was used "...not only in communications issued to the Jewish public when the intention of those issuing the communications was to deceive the Jews in order to minimize the likelihood of resistance, but also in addresses to the outside world and, perhaps more significantly, in internal communications as well, among officials who unquestionably knew (who were themselves sometimes responsible for) the linguistic substitutions stipulated by the language rules." Background By the summer of 1941, Action T4 became widespread public knowledge in Germany (and also in neutral countries and to Germany's enemies), and on August 24, 1941, Hitler ordered the joint chief of the operation Dr. Karl Brandt to halt it due to public protest; however, the operation continued, not only out of the public eye, but also in greater intensity. Hitler did not want to run the risk of an order publicly embarrassing him again and, as a result, the explicit order to carry out the Holocaust was given by him orally. Even if there had been any written instances of this order, they would have almost certainly been destroyed by the Nazis when they realised their defeat was inevitable. Where the Nazis had to document murder, was one of a number of euphemisms used. The Action T4 doctors used ("disinfected") to document the gassing of mentally ill and handicapped individuals. The actual plan to exterminate the Jews of Europe was called ("Final Solution to the Jewish Question"). Other words to describe extermination operations included: ("evacuation") ("expulsion") ("resettlement") ("thinning out" – as in the removal of inhabitants from a